Merge pull request #123 from Tieske/master

minor fix
refactored error handling, less error prone
Improve "see help" messages and always use the name by which the luarocks program was launched.
Make life easier for our friends who are still using VT-100 terminals.
I wonder if LuaRocks runs on Unix System V? :)
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Fix uses of home_config_file when it goes missing due to --force-config.
Accidental workaround was left behind
Merge pull request #124 from Tieske/refactor_builtin_error

refactored error handling, less error prone
Merge pull request #128 from Tieske/removed_win_workaround

Removed windows workaround